Manufacturers of glass sheets, particularly glass sheets formed into various curved shapes for use as automotive windshields, backlites, and sidelites, desire to identify small marks or other defects that are visible on the surface of or within the formed sheets that might be perceived by a human observer, such as the operator or passenger in a vehicle in which the glass may be mounted as the windshield, backlite, or sidelite.
Various types of glass sheet optical inspection systems are known. One known optical inspection system is disclosed in United States Application Publication No. 2012/0098959 A1, which application is also assigned to the assignee of the invention disclosed herein. This disclosed optical inspection system may be implemented in either a laboratory (i.e., off-line) or an in-line configuration in which the inspection system is mounted to inspect glass sheets to measure and evaluate the amount of transmitted optical distortion, as well as to detect and measure small defects in the formed sheets as they are being conveyed in a processing system, such as, for example, is disclosed in United States Application Publication No. 2016/0257598 A1, which application is also assigned to the assignee of the invention disclosed herein. This disclosed system includes a glass sheet acquisition and positioning mechanism to remove the glass sheet, and retain and accurately position the sheet in a preselected position, such as, for example, the installation angle of the glass sheet in a vehicle, to more accurately measure the transmitted distortion that might be perceived by a vehicle occupant.
In these and other known systems, however, the data from a single camera, acquired at a single preselected position, is utilized for both the transmitted optical distortion and the small defects analyses. While this approach minimizes the amount and frequency of image data acquisition, the optimal image acquisition parameters (e.g., image resolution, position of glass sheet relative to the background screen, background screen pattern) differ for these two analyses.
It may be useful to utilize a method and apparatus that is optimized for, and dedicated solely to, detecting and measuring small defects in glass sheets.